Certain xerographic systems containing as components non-bio-degradable materials, such as for example, polymers prepared from bisphenol A are known. The environmental issues relating to the use of bisphenol A and other toxic chemicals have been well documented, especially as these chemicals adversely affect human beings, animals, trees, plants, fish, and other resources. Also, it is known that non-biodegradable materials and toxic chemicals usually cannot be safely recycled, are costly to prepare, cause the pollution of the world's water, add to the carbon footprint, and reduce the oil and coal reserves. Thus, desirable is the development of green materials, such as polymers that are biodegradable, that minimize the economic impacts and uncertainty associated with the reliance on petroleum imported from unstable regions, and that reduce the carbon footprint by, for example, about a 50 percent reduction.
Biodegradable (bio, or bio-based) polymers have been referred to as a group of materials that respond to the action of enzymes, and that chemically degrade by their interaction with living organisms. Biodegradation may also result from chemical reactions that are initiated by photochemical processes, oxidation and hydrolysis, and other environmental factors. Also, biodegradable polymers can include a number of synthetic polymers that possess chemical functionalities present in naturally occurring compounds. However, a number of these polymers can be costly to prepare, may not be fully biodegradable, and may decompose resulting in emitting carbon to the environment.
The transfer of toner developed images from a photoconductor to an image support substrate, like a sheet of paper, involves overcoming cohesive forces holding the toner particles to the photoconductor. The interface between the photoconductor surface and the image support substrate may not in many instances be optimal, thus, in the transfer process when spaces or gaps exist between the developed image and the image support substrate developed image quality is decreased. Therefore, there is a tendency for toner, or portions thereof, not to transfer across these gaps causing variable transfer efficiency, which in turn can create areas of low transfer, or no transfer resulting in image transfer deletion where relevant information is not reproduced on the image support substrate.
Also, non-flat or uneven image support substrates, such as paper, that have been mishandled, left exposed to the environment, or previously passed through a fixing operation, with heat and/or pressure fusing, tend to result in poor contact with the surface of the photoconductor. Further, in the event the copy sheet is wrinkled it will not be in sufficient, uniform, and continuous contact with the photoconductor surface and spaces, or air gaps will form between the developed image on the photoconductive surface and the image support substrate.
Cumbersome mechanical devices that force the image support substrate into contact with the image bearing surface have also been incorporated into xerographic transfer systems. These devices, such as rollers, have been used to force the image support substrate, or a sheet of paper into intimate and substantially uniform contact with the image bearing surface. For example, there can be selected devices containing an electrically biased transfer roll system in an attempt to minimize image deletions.
Image transfer deletion is undesirable in that portions of the developed image may not be fully reproduced on the substrate to which the image is transferred. For example, a transfer assist blade that contacts the photoconductor will in many instances retrieve residual dirt and toner from the photoconductor surface that can be conveyed to the transfer assist blade resulting in unacceptable, or poor print quality defects. Further, continuous frictional contact between the blade and the photoconductor may cause permanent damage to the photoreceptor.
In single pass color machines, it is desirable that minimal disturbance to the photoconductor results so that motion errors are not formed along the photoconductor causing image quality and color separation registration problems. This disturbance, which is often referred to as trail edge flip, can cause image defects on the substrate sheet due to the motion of the sheet during transfer generated by energy released because of the bending forces of the sheet. Thus, in machines which handle a large range of paper weights and sizes, it is difficult to have a sheet guide which can properly position any weight and size sheet while not causing the sheet to oscillate after having come into contact with the photoconductor.
With multicolor electrophotography, where there is selected a machine architecture which comprises a plurality of image forming stations, toner developed images can be of poor image quality because of the insufficient transfer of the toner particles present on a photoconductor. One example of the plural image forming station architecture utilizes an image-on-image (IOI) system in which the photoconductor member is recharged, reimaged and developed for each color. The charging, imaging, developing and recharging, reimaging and developing, all followed by transfer of the image to paper, can be completed in a single revolution of the photoconductor referred to as single pass, while multipass architectures form each color separation with a single charge, image and develop sequence, with separate image transfer operations for each color.
There is a need for transfer assist members that substantially avoid or minimize the disadvantages illustrated herein.
Further, there is a need for transfer assist members that include a check film comprising a more environmentally acceptable polymer.
Also, there is a need for transfer assist members that are wear resistant and that can be used for extended time periods without being replaced.
Additionally, there is a need for transfer assist members that possess excellent mechanical properties, desirable glass transition temperatures, and acceptable modulus especially as compared, for example, to the environmentally damaging polyethylene terephthalates.
There is also a need for transfer assist members that permit the continuous and uniform contact between a photoconductor and the substrate to which a developed toner image is to be transferred, and processes for enhancing contact between a copy sheet substrate and a developed image positioned on a photoconductive member.
Yet another need resides in providing xerographic printing systems, inclusive of multi-color generating systems, where there is selected a transfer assist member that maintains sufficient constant pressure on the substrate to which a developed image is to be transferred, thus substantially eliminating air gaps between the substrate and the photoconductor, which gaps can cause air breakdown in the transfer field.
Further, there is a need for transfer assist members that enable suitable and full contact of the developed toner image present on a photoconductor with a substrate to which the developed image is to be transferred.
Additionally, there is a need for transfer assist members that contain durable compositions that can be economically and efficiently manufactured, and where the amount of energy consumed is reduced.
Yet additionally, there is a need for a multilayered transfer assist member that includes as one layer an environmentally acceptable bio-based generated polymer check film located on the side exposed to xerographic corona charging wires.
Also, there is a need for transfer assist members where the transfer assist member check film layer can be generated roll to roll by extrusion processing.
Further, there is a need for transfer assist members with a combination of excellent durability that exert sufficient constant pressure on a substrate and permit the substrate to fully contact the toner developed image on a photoconductor, which members provide mechanical pressure from, for example, about 20 to about 30 percent of its function, and electrostatic pressure/tailoring of, for example, from about 70 to about 80 percent of its function, and where there results excellent transfer of a developed image to a suitable substrate, such as, for example, from about 90 percent transfer to about 100 percent transfer, from about 95 percent transfer to about 100 percent transfer, from about 90 percent transfer to about 98 percent transfer, or from about 95 transfer to about 99 percent transfer, and where blurred final images are minimized or avoided.
Moreover, there is a need for composite transfer assist blades that overcome or minimize the problems associated with a single component blade which does not provide sufficient consistent contact force to the back of a substrate to enable complete image transfer, and causing developed image deletions and color shift.
Yet, there is another need for transfer assist members useful in electrophotographic imaging apparatuses, including digital printing where the latent image is produced by a modulated laser beam, or ionographic printing where charge is deposited on a charge retentive surface in response to electronically generated images or stored images.
These and other needs are believed to be achievable with the disclosed transfer assist members.